Circuit interrupter



Feb. 25, 1936.

H. L. RAWLINS CIRCUIT INTERRUPTER Filed Sept. 13, 1934 2 Sheets-Sheet l5 2 i F M 3 l E 3 2 M a z 3 33 {A f INVENTOR Her-672 L. EawZz'rzsATTORNEY WITNESSES I H. L. RAWLINS 2,032,149

CIRCUIT INTERRUPTER Filed Sept. 13, 1934 2 Sheets-Sheef 2 Maynef/cMa/er/a/ Feb. 25, 1936.

f/erberz L. PawZz'n s.

ATTO R N E Patented Feb. 25, 1936 CIRCUIT INTERBUPTER Herbert L.Rawlins, Wilklnsburg, Pat, assignor to Westinghouse Electric isManufacturing Company, East Pittsburgh, Pa a. corporation ofPennsylvania Application September is, 1934, Serial No. 743,845

25 Claims.

My invention relates generally to circuit interrupters and particularlyto circuit breakers wherein the arc which is established incident to theopening of the controlled circuit is extinguished by the action of anexpulsive blast of arc extinguishing gas. Y

Devices of this type are generally used for protecting networkdistribution systems, and in this service they are subjected to veryexacting and somewhat conflicting operational requirements. One of theserequirements is the almost imperative necessity that the devices shallbe capable of efficiently extinguishing arcs of both large and smallmagnitude currents. This arises from the fact that the normal overloadcurrents which flow in the ordinary network distribution system areusually of relatively small current magnitude, while the short circuitcurrents may reach a very large magnitude: Despite this necessity foreilicient operation over a wide range of current values, commerciallysuccessful devices must be relatively inexpensive both in first cost andin maintenance cost, due to the large numbers which are used on even asmall distribution system. The devices must, of course, be absolutelyreliable in operation, and it is desirable that they shall not utilizean inflammable liquid for extinguishing the arc formed during aswitching operation in order that the fire hazard shall be minimized.

The principal object of my invention, therefore, is to provide animproved circuit interrupter of the expulsion type which shall be simplein design, reliable in operation, and inexpensive to manufacture and tcservice.

A further object of my invention is to provide a circuit interruptingdevice of the above-mentioned type which shall utilize a minimum ofmoving parts, and which shall eiTect the extinguishment of the arc whichis established.in--

cident to the opening of the controlled circuit by means of a blast ofarc extinguishing gas, which is evolved from a solid material positionedadjacent the arc path.

The principal field for immediate application of my invention is inconjunction with expulsion circuit interrupting devices which utilize apartially enclosed arc passage that is lined with a solid material forevolving arc extinguishing gas during the circuit interruptingoperation. The eiilciency oi. operation of these devicesdepend to alarge extent upon the intimacy of contact which is achieved during thecircuit interrupting operation between the arc and the gas evolvingwalls of the arcpassage. At first glance, it

might appear that this necessity for securing intimate contact betweenthe arc and the gas evolving lining of the arc passage would prevent noparticular difllculties, since the arc passage could .be made smallenough to assure lnti mate contact between the walls thereof and the arefor the lowest current magnitude arcs which the device would ordinarilybe called upon to interrupt.

Unfortunately, however, the problem is not so simply solved, since it ispossible to make the cross sectional area of the arc passage too small,in which case, the volume of gas generated may be sufilciently large tocause an actual rupture oi. the walls of the device, due to the pressureformed therein. It has been demonstrated in the prior art structuresthat a satisfactory device, which is capable of interrupting arcs ofwidely varying current magnitude, must utilize a plurality of arcpassages. For most presentday circuits, two passages have been foundsumcient, one of relatively small cross-sectional area for interruptingthe low magnitude arcs and one of somewhat larger cross-sectional areafor interrupting the higher magnitude arcs.

When a plurality of arc passages is used, it is necessary to providemeans for assuring that the arc shall be drawn within that passage whichis best suited for effecting its extinguishment, because if smallcurrent magnitude arcs are drawn within the arc passage which is capableof interrupting large current magnitude arcs, it is probable thatinsufllcient gas will be evolved to effect the extinguishment of thatarc, and the circuit may never be interrupted at all.

Various arrangements have been proposed for assuring that thearc will beestablished in the proper passage, but few of these have been as simpleand as rugged as might be desired, and it is a further object of myinvention to provide a simple means for use with circuit interruptershaving a plurality of arc passages, one of which is of greater areinterrupting capacity than the other, for assuring that the arc shall bedrawn within that passage which is best suited for effecting itsextlnguishment.

It is a still further obiect of my invention to eliminate any necessityfor causing the arc to transfer from one passage to the other during theoperation of the device the are drawing means of my invention to beresponsive to the current flowing in the circuit controlled by theinterrupter in order that only one are shall be drawn during the circuitinterrupting operation, and that that are shall be drawn in the properpassage.

In .the following description of one embodiment of my invention, I havedescribed how my. invention may be applied to a dry-type expulsioncircuit interrupter which utilizes a pair of arc passages. It isobvious, of course, that the broad principles disclosed may be appliedto numerous other structures, and it is my intention that my inventionshall be limited only by what is exthe line III--III of Fig. 2;

Fig. 4 is a fragmentary perspective view showing the details of thecontact structure of the device shown in Figs. 1 and 2;

Fig. 5 is a sectional view of a modified form of the circuit interruptershown in Figs. 1 and 2;

Fig. 6 is an elevational view of the circuit interrupting device shownin Fig. 5; i

Fig. 7 is an enlarged sectional view taken on the line VII-'V'II of Fig.5;

Fig. 8 is a fragmentary perspective view of the contact structure forthe circuit interrupter shown in Figs. 5 through 7;

Fig. 9 is a fragmentary sectional view on the line IX-IX of Fig. 8;

Fig. 10 is an enlarged fragmentary sectional view on the line X-X ofFig. 5.

Fig. 11 is a modified sectional view of an arc extinguisher similar tothat used in conjunction withv the circuit breaker shown in Figs. 1through 4; and

Fig. 12 is a sectional view taken on the line XII-XII of Fig. 11.

Essentially, the preferred circuit breaker of my invention comprises apair of stationary contact structures 3, a, movable contact structure 5,an actuating means I for moving the contacts to the open and closedcircuit position, 'and a support frame I upon which the several parts ofthe breaker are mounted. The interrupter is of the double-break type andis provided with a suitable arc extinguishing device 9 for each of thetwo breaks. These are extinguishing devices include means for producingan expulsive blast of gas which is adapted to flow longitudinallythrough the arc during the circuit interrupting operation to eifect itsextinguishment.

The frame I, as is shown particularly in Fig. 1, is provided with aguide portion II for supporting the rod member |2 which is afiixed tothe movable armature |3 of the operating solenoid. This armature I3 isnormally biased to the open circuit position by means of a suitablespring I5 and is held in the closed circuit position by the solenoidcoil I! which may be energized by any suitable means. The right-hand endof the rod member I2 is adapted to engage the knee of a pair oftogglelinks 9 and 2| which constitute the operating linkage for the breaker.The lower end of this linkage is pivotally supported on the frame I, andthe upper end engages a suitable push rod 23 which in turn is aflixed tothe movable contact structure 5. The motion of the rod pressly set forthin the claims and by the prior 23 is defined by a suitable guiding means25 forming a part of the frame.

The movable contact structure 5 comprises generally a main frame member21 of conducting material upon which are supported the two main contactrods 29 and the auxiliary contact assemblage 3|. The assemblage 3|includes two contact rods 32 and engages the frame member 21 through alost motion connection which comprises a pair of bolt members 33, forlimiting the amount of lost motion between main frame 2! and theauxiliary contact assemblage 3|, a pair of springs 35 for biasing theauxiliary contact assemblage 3| away from the main frame 21 of thecontact structure, and a magnetic arrangement for rendering the lostmotion connection ineffective upon the occurrence of certainpredetermined conditions. This magnetic arrangement consists of a pairof U-shaped members 31 of magnetic material which are disposed about andrigidly affixed to the main frame 2'! of the contact structure and apair of U-shaped members 39 of magnetic material which are similarlyaffixed. to the main bridging portion 4| of the auxiliary contactassemblage. It is apparent that these U-shaped pieces 31 and 39 ofmagnetic material will be attracted toward each other when the magnitudeof the current flowing through the interrupter reaches avalue capable ofproducing sufficient magneto-motive force to overcome the action of thesprings 35.

The main contact rods 29 and the auxiliary contact rods 32 are bothadapted to move, during the normal operation of the breaker, withinsuitable arc passages 43 and 45, respectively, which are formed withinthe two are extinguishing devices 9. The stationary contact structure 3for each of the two breaks of the device is supported upon the top ofthe cooperating arc extinguishing structures 9 and those structures inturn are supported upon the main breaker frame I.

Each of the stationary contact structures 3 includes a metal plate 41which forms one of the terminals of the device, and a pivotallysupported contact member 49 which is adapted to cooperate with one ofthe main contact rods 29. Springs 5| are provided for biasing thesecontact members 49 in the direction of the cooperating moving contactrods 29, in order to assure adequate contact pressure between theengaging contact surfaces of those members when the breaker is in theclosed circuit position. The auxiliary contact rods 32 engage suitableholes 53 formed within the conducting plates 41 which comprise theterminals of the device. A molded member 55 of insulating materialhaving two raised portions 51 for accommodating the pivotally mountedcontact members 49 is rigidly affixed to the top of the two arcextinguishing devices 9 in order that the upper end of each of the arcpassages 43 and 45 shall be closed during the circuit interruptingoperation. This molded-member has a tie portion 59, likewise ofinsulating material, which extends across the top of the device in orderto give the structure increased rigidity.

The are extinguishing devices 9 are exactiysimilar in construction andare built up of a plurality of circular plates 5|, each of which hasfour equally spaced openings I53 therein for accommodating the throughbolts 55 which serve to hold the arc extinguishing devices together. Inaddition, each of the plates BI is provided with a pair of openings fordefining the two are passages 43 and 45. The lower plate 51, which,similarly to the upper molded member 55, extends across both of thedevices, is considerably thicker than the plates 6i which define themain portion of the arc passages. A suitable opening 59 is provided inthe two contact plates 41 for defining a continuation of the larger ofthe two are passages 43 in order that the main contact rods 29 mayextend therethrough while engaging the pivoted contact members 49. Allof the centrally disposed plates Bi which define the walls of the arcpassages 43 and 45 are preferably formed of fibre or some other materialwhich is capable ofevolving an arc extinguishing gas when placed inproximity to an electric arc. This assures an adequate supply of arcextinguishing gas during the circuit interrupting operation.

The breaker is shown in the closed circuit position in Fig. 2. To openthe circuit, the holding coil ll of the actuating solenoid isdeenergized by some suitable means whereupon the spring i5 initiates themovement of the actuating toggle linkage toward the collapsed position.If the magnitude of the current flowing in the circuit controlled by theinterrupter is incapable of producing sufficient magnetic energizationof the two magnetic circuits formed by the U-shaped magnetic members 31and 39 to overcome the biasing action of the springs 35, the initialportion of the opening movement is effective merely to move the maincontact rods 29 out of engagement with the cooperating members 49 of thestationary contact structures 3. All of the electric current thenflowing through the breaker is carried by the auxiliary contact rods 45,and as the opening operation progresses, an arc is established withineach of the two are passages 45 wherein those rods move. These smallerarc passages 45 are so proportioned that they cause an intimateengagement of even low magnitude current arcs with the evolving wallsthereof, and by virtue of the fact that they are closed at the upper endproduce a blast of arc extinguishing gas which flows downwardly throughthe arc while venting. In the open circuit position, both the auxiliaryand the main contact rods are completely out of engagement operationwith the arc passages.

If the magnitude of the overload current is sufficientto cause theauxiliary contact assemblage 3i to be attracted to the frame 21 of themain contact members 29, the arcs which are estab- 'iished incident tothe opening of the circuit controlled by the device will be initiallyestablished and subsequently drawn within the larger arc passages 43.These passages 43, while incapable of interrupting low magnitude arcs,are capable of interrupting large magnitude arcs with a high degree ofefliciency. The gas evolved from the iining of both are passages duringthe circuit interrupting operation, must vent at the lower portion ofthe device, due to the enclosing of the upper end of each of the arcpassages by the molded member 55.

It will thus be seen that I have provided a circuit interrupting devicewhich is capable of eflicient operation over a wide range of currentvalues. My improved interrupter comprises a. pair of arc passages, oneof which is capable of interrupting large current magnitude arcs but isincapable of interrupting small current magnitude arcs, and the other ofwhich is capable of interrupting small current arcs, and meanswherebyonly one are is created during the circuit interruptingoperation, that are being'initially established and subsequently drawnwithin the passage which is best suited for effecting itsextinguishment.

The walls of the arc extinguishing devices 01' the interrupter describedabove are defined by a plurality of superposed plate sections. This, orcourse, is merely one of the arrangements which may be used. Figs. 11and 12 illustrate a modifled structure which has also been found to beparticularly effective for accomplishing the objects of my invention.This modified structure differs from the arrangement shown in Figs. 1through 3 only in that it comprises a tubular outer member ii ofconsiderable mechanical strength and a cylindrical inner member 13 whichis formed of compressed boric acid, this inner member having a pair ofcylindrical openings 15 and 11 therein for defining the walls of the twoare passages. Compressed boric acid is a particularly satisfactorymaterial for this use; it may readily be compressed into solid blocks ofconsiderable physical strength, and in addition it evolves averyconsiderable quantity of water vapor, a particularly effective areextinguishing gas, when exposed to an electric arc. Boric acid hasanother advantage in that the surface thereof does not become conductingduring the arc extinguishing operation. Further, the fact that the gasis entireiy inorganic in nature and noninfiammable adds much to thesafety and reliability of operation of the device when this form of arcextinguishing structure is utilized.

The modified form of my invention which is shown in Figs. 5 to 10,inclusive, does not difier in its principles of operation from thestructure shown in the other figures of the drawings. The deviceincludes means for defining the walls of a pair of arc passages 8i and83, one of which 8i is capable of interrupting arcs of large currentmagnitude but is incapable of interrupting arcs of small currentmagnitude, and the other of which 83 is capable of interrupting arcs oflow current magnitude. The are passages are both of the so-cailednarrow-slot type, the structural features and operationalcharacteristics of which have been rather completely described in thepatent application of Joseph Slepian, Serial No. 715,817, which wasfiled on March 16, 1934 and which is assigned to the assignee of thisinvention.

This modified .form of my invention utilizes a.

lost motion connection between the are drawing means for the two arepassages, and it likewise utilizes a magnetic means for rendering thislost motion connection inoperative upon the occur rence of certainpredetermined conditions.

Referring more particularly to the drawings, it will be seen that thismodified form of my invention comprises a base 85 of insulating materialupon which the other structural features of the interrupter aresupported, a pair of main stationary contact members 81, a bridgingmember 89 for completing the electrical circuit between the mainstationary contact members, an are extinguishing device 9| whichincludes means for defining the two narrow slot arc passages BI and 83,auxiliary contact means 93 for drawing an arc in either of thosepassages, and an actuating means 95 for the are drawing contacts and themain bridging member 89. The main and the auxiliary moving contacts aresupported upon link members 91 and99 which are pivotally fastened to themain supporting base I of the interrupter.

The actuating mechanism 95 is so arranged that the main bridging member89 is always moved to the open circuit position before the electricalcircuit through the auxiliary contacts parts in their properrelationship.

is broken. This means for accomplishing this consists essentially in alink member |0I (shown particularly in Fig. 10) which is provided with aslot I03 wherein the support link 99 for the auxiliary contact membersmoves, a suitable spring I05 being positioned within this slot I03 forbiasing the auxiliary contacts into engagement with the cooperatingstationary contact members therefor. The outer end of the link IOIpivotally engages an operating link I01 which is connected to theremainder of the actuating mechanism (not shown).

The auxiliary contact structure is shown particularly in Figs. 5, 8, and9, and comprises in general a pair of hammer-shaped members I09 and III,one of which (I09) is considerably thicker than the other. The thickerof these two members is welded or otherwise rigidly affixed to the upperend of the auxiliary contact support link 99, and the thinner of the twomembers is pivotally supported upon the link 99 in order that it shallbe relatively movable therewith. The limits of this relative motion isdefined by a lost motion connection, as in the previously describedstructure.

The auxiliary contact members I09 and I I I are adapted to cooperatewith L-shaped arc horns I I3 and H5 disposed within each of the two arepassages 8| and 83 in order to complete the electrical circuit throughthe device. One of the arcing horns I I3 and one of the arcing horns II5 is electrically connected to one of the stationary contacts 87 andthe other of each of the two pairs of arcing horns H3 and II5 iselectrically connected to the moving contact assemblage. Thus during thecircuit interrupting operation the arc is established between one of thearcing horns within one of the arc passages within the arc extinguishingdevice and the cooperating moving contact I09 or I I I and is thentransferred to the two arcing horns within that passage. The arcinghorns H3 and H5 are so shaped that the arc is moved by virtue of themagnetic reactions set up therein.

The are extinguishing device 9| is shown particularly in Figs. 5 and 7and includes a pair of fiat members II! of insulating material fordefining the outer walls thereof, and a. centrally disposed member H8,likewise of insulating material, for defining an inner wall which iscom-.- mon to both of the two are passages 8| and 83. Spaced members 9of insulating material and bolts |2| are provided for assembling thevarious It will be seen that both of the arc passages 8| and 83 comprisenarrow slots, the dimensions of which are defined by a pair ofsubstantially parallel wall members of considerable surface area. 4

Both of the arc passages 8| and 83 are lined with a plurality of membersI23 of a solid material which is capable of evolving an areextinguishing gas when placed in proximity to an electric arc. Thesemembers are shaped and disposed like tile and are cemented or otherwiserigidly affixed to the wall defining members I I7 and H8 and arepreferably of compressedboric acid. During the operation of the breakerthey serve to provide a blast of arc extinguishing gas for extinguishingthe arc formed incident to the opening of the controlled circuit.

The arc passage 83 is considerably narrower than the other passage 8| inorder that that passage shall be capable of extinguishing arcs of smallcurrent magnitude. The other are passage 8| is particularly adapted forextinguishing arcs of large current magnitude and is, in fact, incapableof extinguishing arcs of small current magnitude, due to its inabilityto effect an intimate contact between the arc and the gas evolvinglining thereof.

In order that the low current magnitude arcs shall be drawn only withinthe smaller capacity are passages 83, a lost motion connection isprovided between the main actuating link 99 for the are drawing meansand the narrower of the two arc drawing members. This lost motionconnection is shown particularly in Figs. 8 and 9, and comprises aU-shaped member I25 of magnetic material rigidly affixed to the widerarc drawing member I09 (the one which is in turn rigidly affixed to theactuating link 99 for the are drawing contact structure), an armaturemember I2? likewise of magnetic material rigidly aifixed to the narrowerarc drawing members III, a bolt I 29 for limiting the'relative motion ofthe two arc drawing members, and a spring I3I for biasing the narrowermember III away from the wider member I 09 in the direction of thecooperating arcing horn I I 5. By this arrangement, the circuit isalways finally interrupted, and the arc incident to that interruption,is always initially drawn within the narrower arc passage 83 unless thecurrent magnitude is sufiiciently largev to cause the arc drawingmembers I09 and III to move as a unit, in which case it is drawn withinthe wider arc passage M.

The operation of this modified form of my invention is practicallyidentical with the operation of the previously described embodiment. Asthe operating mechanism moves the main actuating link I01 toward theopen circuit position, the bridging member 89 is moved out of engagementwith the cooperating stationary contact members 81, and all of thecurrent flowing through the device is then caused to fiow through theauxiliary contact structure. If the current magnitude is low, thethicker auxiliary contact member I09 is next moved out of engagementwith its cooperating arcing horn I I3, and subsequently, the timedepending upon the amount of lost motion in the lost motion connection,the auxiliary contact I disengages its cooperating arcing horn I I5 andcauses the arc incident to the opening of the control circuit to bedrawn within the narrower arc passage 83.

Shortly thereafter, the end of the arc which has previously existed uponthe narrow contact member I is transferred to the other arcing horn 5,that horn being electrically connected to the moving contact structure,as illustrated diagrammatically in Fig. 5. The arrangement of the arcinghorns is such that the arc is moved upwardly within the narrow slotpassage 83 by the magnetic reactions set up, and by virtue of theintimate engagement produced between the arc and the lining members I23of the passage, a large quantity of vapor is evolved. This vapor inventing flows outwardly through the arc in a lateral direction andefiects its extinguishment within a very short period of time.

If the current magnitude in the controlled cir- Y by being caused toflow through the arc in venting 'eii'ects the extinction thereof withina very short period of time, usually at the next zero point in thecurrent wave' if an alternating cur rent arc is being interrupted.

In the foregoing, I have described how my invention may be applied totwo particular forms of dry-type circuit interrupting devices whichutilize a plurality of arc passages of different are extinguishingcapacity for extending the eifective range over which such devices maybe used. I have shown how a simple structure which utilizes a lostmotion connection and a magnetic means responsive to the current flowingin the controlled circuit for rendering that connection inoperative uponthe occurrence of predetermined conditions may be utilized for assuringthat the arc incident to the opening of the controlled circuit shall beestablished within that are passage which is best suited for efiectingits extinguishment. The advantagesoi this arrangement in simplicity andin making possible .a more reliable and less expensive deviceareobvious.

Moreover, I have shown how the features of my invention may be readilyapplied to certain existing forms of circuit interrupting devices,thereby effecting a considerable improvement in the operationalcharacteristics thereof. In addition, I have disclosed certain preferredstructural arrangements which are particularly suitable for carrying outthe objects of my invention.

It will be apparent to those skilled in the art that numerousmodifications of my invention will be possible without departing fromthe broad features thereof, audit is my desire that the language of theaccompanying claims shall be accorded the broadest reasonableconstruction. For example, it is my wish that these claims should coverdevices wherein only a single arc extinguishing device is used, anddevices which utilize a liquid for securing the blast oi areextinguishing gas during a circuit interrupting operation.

I claim as my invention:

1.In a device for interrupting an electrical circuit; means for definingthe walls of a pair of arc passages; one of said are passages beingcapable of extinguishing arcs of large current magnitude but beingincapable of extinguishing arcs of small current magnitude, and theother of said passages being capable of extinguishing arcs of smallcurrent magnitude; and electro-responsive' means for causing the arewhich is established incident to the opening of said circuit by saidinterrupter to be initiated and then drawn only within that passagewhich is best suited for effecting its extinguishment.

2. In a device for interrupting an electrical circuit; means fordefining the walls of a pair of arc passages; one of said are passagesbeing capable of extinguishing arcs of large current magnitude but beingincapable of extinguishing arcs of small current magnitude, and theother of said passages being capable oi extinguishing arcs of smallcurrent magnitude; and means for drawing the are which is establishedincident to the opening of the circuit controlled by said device withinonly one of said passages, said are passages; one of said arc passagesbeing capable of extinguishing arcs of large current magnitude but beingincapable of extinguishing arcs of small current magnitude, and theother of said passages being capable of extinguishing arcs of smallcurrent magnitude; and means for drawing the are which is establishedincident to the opening of the circuit controlled by said device withinonly one of said passages; said are drawing means including conductingmeans movable through each of said passages during the circuit openingoperation, means for actuating said conducting means, and magnetic meansresponsive to the current flowing in the circuit controlled by saiddevice for causing arcs of large current magnitude to be initially drawnwithin said passage of large arc interrupting capmity and for causingarcs of small current magnitude to be initially drawn within saidpassage which is capable of extinguishing arcs of small currentmagnitude.

4. a device for interrupting an electrical circuit; means of a solidmaterial which is capable of evolving an arc extinguishing gas whenplaced in proximity to an electric arc for defining the walls of a pairof arc passages; one of said passages being so proportioned that it iscapable of extinguishing arcs of large current magnitude but isincapable of extinguishing arcs of small current magnitude, the other ofsaid passages being capable of extinguishing arcs of small currentmagnitude; and electro-responsive means for causing the are which isestablished incident to the opening of said circuit by said device to beestablished only within that passage which is best suited for efiectingits extinguishment.

5. In a device for interrupting an electrical circuit; means of a solidmaterial which is capable of evolving an arc extinguishing gas whenplaced in proximity to an electric arc for defining the walls of a pairof arc passages; one of said passages being so proportioned that it iscapable of extinguishing arcs of large current magnitude but isincapable of extinguishing arcs of small current magnitude, the other ofsaid passages being capable of extinguishing arcs of small currentmagnitude; and means for causing the arc which is established incidentto the opening of the circuit controlled by said device to be drawnwithin only one of said passages; said are drawing means includingconducting means movable through each of said passages duringthe circuitopening operation and magnetic means responsive to the current flowingthrough the circuit controlled by said device for assuring that said arcis initially established and is drawn only within that passage which isbest suited for effecting its extinguishment.

6. In a device for interrupting an electrical circuit, means defining apair of arc passages, actuating means for said device, and means wherebythe arc which is established incident to the opening of the circuitcontrolled by said device is initially drawn within one of said passagesprovided that the magnitude of the current flowing in the circuitcontrolled by said device does not exceed a predetermined value and isinitially drawn within the other of said passages if the magnitude ofsaid current exceeds said predetermined value.

7. In a device for interrupting an electrical circuit, means defining apair of arc passages of different are interrupting capacity, conductingmeans movable through each of said passages during the operation oi saiddevice, a single actuating means for said conducting means, and meanswhereby the are which is established incident to the opening of thecircuit controlled by said device is initially drawn within one of saidpassages provided that the magnitude of the current flowing in thecircuit controlled by said device does not exceed a predetermined value,and is initially drawn within the other of said passages if themagnitude of said current exceeds said predetermined value.

8. In a device for interrupting an electrical circuit, means defining apair of arc passages of different arc interrupting capacity, conductingmeans movable through each of said passages during the operation of saiddevice, a single actuating means for said conducting means, and magneticmeans responsive to the current flowing in the circuit controlled bysaid device for causing the are which is established incident to theopening of said circuit to be initially established and subsequentlydrawn within the arc passage of lesser arc interrupting capacityprovided that the magnitude of said current does not exceed apredetermined value, and if the magnitude of said current does exceedsaid predetermined value to cause said are to-be initially establishedand subsequently drawn within the arc passage of greater areinterrupting capacity.

9. In an expulsion device for interrupting an electrical circuit, meansdefining the walls of a pair of arc passages, at least a portion of theinner surfaces of said wall defining means being lined with a solidmaterial that is capable of evolving an arc extinguishing gas whenexposed to an electric are; means for closing one end of said arepassages during the circuit interrupting operation, the other end ofsaid passages being open during the circuit interrupting operation;actuating means for said device; and means whereby the are which isestablished incident to the opening of the circuit controlled by saiddevice is initially drawn within one of said passages provided that themagnitude of the current flowing in the circuit controlled by saiddevice does not exceed a predetermined value, and is initially drawnwithin the other of said passages if the magnitude of said currentexceeds said predetermined value.

10. In an expulsion device for interrupting an electrical circuit, meansdefining the walls of a pair of arc passages of difiering arcinterrupting capacities, at least a portion of the inner surfaces ofsaid wall defining means being lined with a solid material that iscapable of evolving an arc extinguishing gas when placed in proximity toan electric a3; means for closing one end of each of said are passagesduring the circuit interrupting operation, the other end of saidpassages being open during the circuit interrupting operation; andelectro-responsive means for causing the are which is establishedincident to the opening of said circuit by said device to be initiallyestablished only within that passage which is best suited for effectingits extinguishment.

11. In an expulsion device for interrupting an electrical circuit, meansdefining the walls of a pair of arc passages of difi'ering arcinterrupting capacities, at least a portion of the inner surfaces ofsaid wall defining means being lined with a .solid material that iscapable of evolving an arc extinguishing gas when placed in proximity toan electric are; means for closing one end of each of said are passagesduring the circuit interrupting operation, the other end of saidpassages being open during the circuit interrupting operation; andmagnetic means responsive to the current flowing in the circuitcontrolled by said device for causing the arc which is establishedincident to the opening of said circuit to be initially established andsubsequently drawn within the arc passage of lesser arc interruptingcapacity provided that the magnitude of said current does not exceed apredetermined value, and if the magnitude of said current does exceedsaid predetermined value to cause said are to be initially establishedand subsequently drawn within the arc passage of greater areinterrupting capacity.

12. In a device for interrupting an electrical circuit; means fordefining the walls of a pair of arc passages; one of said arc passagesbeing capable of extinguishing arcs of large current magnitude but beingincapable of extinguishing arcs of small current magnitude, and theother of said passages being capable of extinguishing arcs of smallcurrent magnitude; at least a portion of each of said are passages beinglined with a solid material consisting chiefly of boric acid, andelectro-responsive means for causing the arc which is establishedincident to the opening of said circuit by said interrupter to beinitiated and then drawn only within that passage which is best suitedfor eiiecting its extinguishment.

13. In a device for interrupting an electrical circuit; means fordefining the walls of a pair of arc passages; one of said arc passagesbeing capable of extinguishing arcs of large current magnitude but beingincapable of extinguishing arcs of small current magnitude, and theother of said passages, being capable of extinguishing arcs of smallcurrent magnitude; at least a portion of each of said arc passages beinglined with a solid material consisting chiefly of boric acid; and meansfor drawing the are which is established incident to the opening of thecircuit controlled by said device within only one of said passages, saidare drawing means including conducting means movable through each ofsaid passages during the circuit opening operation, means for actuatingsaid conducting means, and magnetic means responsive to the currentflowing in the circuit controlled by said device for causing arcs oflarge current magnitude to be initially drawn within said passage oflarge are interrupting capacity and for causing arcs of small currentmagnitude to be initially drawn within said passage which is capable ofextinguishing arcs of small current magnitude.

14. In a device for interrupting an electrical circuit; means fordefining the walls of a pair of arc passages; one of said arc passagesbeing capable of extinguishing arcs of large current magnitude but beingincapable of extinguishing arcs of small current magnitude, and theother of said passages being capable of extinguishing arcs of smallcurrent magnitude; at least a portion of each of said are passages beinglined with a solid material consisting chiefly of boric acid; and meansfor causing the arc which is established incident to the opening of thecircuit controlled by said device to be drawn within only one of saidpassages; said are drawing means including conducting means movablethrough each of said passages during the circuit Opening operation, andmagnetic means responsive to the current flowing through the circuitcontrolled by said device for assuring that said are is initiallyestablished and is drawn only within that pas- 7 said are to beestablished within that passage which is best suited for effecting itsextinguishment.

16. In a circuit interrupter, means defining a plurality of wall membersof considerable surface area, meansfor spacing said wall members inproximity to each other to define the opposed walls of a pair of narrowarc passages, at least a portion of each of said are passages beinglined with a solid material that is capable of evolving an arcextinguishing gas when placed in proximity to an electrical are, one ofsaid are passages having a greater arc interrupting capacity than theother of said passages, separable contact means for opening and forclosing the electrical circuit through said interrupter, andelectroresponsive means for causing the are which is establishedincident to' the separation of said separable contact means to beestablished within that passage best suited for effecting itsextinguishment.

17. In a circuit interrupter, means defining a plurality of 'wallmembers of considerable surface area, means for spacing said wallmembers in proximity to each other to define the opposed walls of a pairof narrow arc passages, one of said are passages having a greater areinterrupting capacity than the other, means for drawing the are which isestablished incident to' the opening iof the circuit controlled by saiddevice within only one of said passages, said are drawing meansincluding conducting means movable through each of said passages, andmagnetically responsive means for so controlling the movement of saidconducting means that said are is initially established in that passagewhich is best, suited for efi'ecting its extinguishment.

18. In a circuit interrupter, means defining a plurality of wall membersof considerable surface area, means for spacing said wall members inproximity to each other to define the opposed walls of a pair of narrowarc passages, one, of said arc passages having a greater arcinterrupting capacity than the other, and means for drawing the arcwhich is established incident to the opening of the circuit controlledby said device within only one of said passages, said arc drawing meansincluding conducting means movable through each of said passages duringthe circuit opening operation, means for actuating said conductingmeans, and magnetic means responsive to the current flowing in thecircuit controlled by said device for causing arcs of large currentmagnitude to be initially drawn within said passage of large arcinterrupting capacity and for causing arcs of small current magnitude tobe initially drawn within said passage which is capable of extinguishingarcs of small current magnitude.

19. In a device for interrupting an electrical circuit, means defining apair of arc passages, conducting means movable in one of said passages,a second conducting means movable in the other of said passages, asingle actuating means for said conducting means, a lost motionmechanical connection between one of said conducting means and saidactuating means, and means responsive to the current fiowing in thecircuit controlled by said device for rendering said lost motionconnection inoperative upon the occurrence of predetermined conditions,the arc which is formed incident to the opening of the circuitcontrolled by said device being initially established and extinguishedwithin one of said passages when said lost motion connection isoperative, and being initially established and extinguished within theother of said passages when said lost motion connection is renderedinoperative.

20. In a device for interrupting an electrical .circuit, meanscomprising a plurality of superposed plates at least some of which areof insulating material for defining the walls of a pair of arc passagesof different are interrupting capacity, and means for causing the arewhich is formed incident to the opening of the circuit controlled bysaid device to be initiated and then drawn only within that passagewhich is best suited for effecting its extinguishment.

21. In a device for interrupting an electrical circuit, means comprisinga stack of superposed plates for defining the walls a pair of arcpassages of different arc interrupting capacity, at least some of saidplates being formed of a material which is capable of evolving an arcextinguishing gas when exposed to an electric arc, and means for causingthe are which is formed incident to the opening of the circuitcontrolled by said device to be initiated and then drawn only withinthat passage which is best suited for efiecting its extinguishment.

22. In electrical circuit interrupting apparatus, a pair of circuitinterrupting devices of different are extinguishing capacities, each ofwhich is movable to an open and to a closed circuit position, means forelectrically connecting said devices in parallel, actuating means forsaid apparatus, which means causes both of said devices to move to theopen circuit position during each circuit interrupting operation ofsaid-apparatus, and magnetic meansfor controlling the sequence ofoperation of said devices so that the electrical 'circuit through saidapparatus shall always be opened by the device best suited forextinguishv ing the are formed incident thereto.

23. In electrical circuit interrupting apparatus, a pair of circuitinterrupting devices of difiering circuit interrupting capacity, each ofsaid devices including contact means movable to an open and to a closedcircuit position, means for electrically connecting said devices inparallel, actuating means for said apparatus, which means causes both ofsaid devices to move to the open circuit position during each circuitinterrupting operation of said apparatus, and elec-' tro-responsivemeans for controlling the sequence of operation of said devices in orderthat the circuit controlled by said apparatus shall finally beinterrupted by that device which is best suited for effecting suchinterruption.

24. In electrical apparatus, a pair of circuit interrupting devices ofdifferent circuit interrupting capacity, one of said devices beingcapable of extinguishing arcs of large current magnitude but beingincapable of extinguishing arcs of small current magnitude, the other ofsaid devices being capable of extinguishing arcs of small currentmagnitude, and electro-responsive means for causing the are which isestablished incident to the opening of the electrical circuit throughsaid apparatus to be initiated and then drawn by that device which isbest suited for effecting its extinguishment.

25. In electrical circuit interrupting apparatus, a pair of circuitinterrupting devices of different circuit interrupting capacity, one ofsaid devices being capable of extinguishing arcs of large currentmagnitude but being incapable of extinguishing arcs of small currentmagnitude and the other of said devices being capable of extinguishingarcs of small current magnitude, each of said devices including a pairof separable contacts, means for-electrically connecting said devices inparallel, actuating means for said apparatus which causes both of saidpairs of contacts to move to the open circuit position during eachcircuit interrupting operation of said apparatus, and electro-responsivemeans for controlling the sequence of separation of said pairs ofcontacts in order that the-circuit controlled by said apparatus shall beinitially opened and finally interrupted by that device which is best 10suited for efiecting such interruption.

HERBERT L. RAWLINS.

